Current methods of calculating and determining stiffness profiles for shafts or beams are commonly based on several assumptions based on the material and the method of bending the beam or shaft. For example, many techniques are based on the assumption that the flexural rigidity of the beam or shaft is continuous along the entire length of the beam or even sub-sections of the shaft. This, however, may not be true in many instances where the cross-sectional area or material properties of the beam are changing along its length. Some current testing methods also commonly utilize a three-point bending test that applies a load to the center of a sub-section of a beam or shaft and forms a “U-shape” deformation. This type of test is common since the associated equations can be relatively simple to solve. However, these simple equations often rely on several assumptions such as the stiffness being constant over the sub-section, deflections being largest as the center and overall deflections being small. These types of assumptions lose accuracy when deflections are large in comparison to the length of the beam and the stiffness profile and material properties are non-constant, as is the case in several beams or shafts.